A known image forming apparatus includes a developing chamber and a buffer. The developing chamber includes a developing sleeve. The buffer contains developer to be supplied to the developing chamber. The buffer includes an agitator member that is rotated to supply the developer to the developing chamber. The buffer also includes an agitator gear for rotating the agitator member. The agitator gear is rotated by drive force from a drive unit. The drive unit includes a pendulum gear configured to contact, e.g., engage, and be separated, e.g., disengage, from the agitator gear by forward and reverse rotation of a gear in the drive unit.
A known process unit includes a process frame and a toner box. The process frame includes a developing unit including a developing roller. The toner box is configured to be attached and removed relative to the process frame. The process frame further includes a coupling gear and a drive gear. The drive gear rotates by receiving drive force from the coupling gear, and transmits the drive force to a transmission gear of the toner box. The toner box includes an agitator. The agitator rotates by receiving the drive force from the transmission gear. As the agitator rotates, the developer in the toner box is supplied to the developing roller in the process frame.